JPH04100866A - Antistatic coating composition - Google Patents

Abstract

PURPOSE:To realize the formation of a film excellent in adhesion to the surface of inorganic or plastic material and also excellent in electroconductivity when heated at low temperatures by mixing a cohydrolyzate of an alcoholic silica sol and a metal compound with a fluoride as the conductivity improver. CONSTITUTION:The title composition comprises a cohydrolyzate of an alcoholic silica sol and a metal compound, obtained by cohydrolyzing a hydrolyzable silicon compound and a cohydrolyzable metal compound in an alcohol solvent, and a fluoride. As the hydrolyzable silicon compound, organic silicates are useful. The preferable cohydrolyzable metal compound may include chlorides and alkoxides of tin, antimony, indium, etc. Among the preferable fluorides are metal fluorides, hydrogen fluoride, ammonium fluoride, etc.

Description

Detailed Description of the Invention [Objective of the Invention 1 (Industrial Application Field) The present invention provides an alcoholic silica sol obtained by co-hydrolyzing a hydrolyzed silicon compound and a conductive metal compound in an alcohol droplet. A novel antistatic coating composition comprising a cohydrolyzate of a metal compound and a specific conductivity improver.

More specifically, it is possible to form a transparent inorganic coating with anti-static properties that does not deteriorate in performance even under low humidity conditions, or with anti-shock properties, at an extremely low temperature of heating and drying at around 150°C. The present invention relates to an antistatic coating composition.

(Conventional technology and its limitations) Previously, JP-A-46-37119, JP-A-60109
No. 134, JP-A No. 61-55164, etc., a composition obtained by hydrolyzing a hydrolyzable silicon compound represented by Si (OR) 4 (silicate ester) is
It is known to form an inorganic film having antistatic, anti-scald, and surface protective properties on glass or plastic surfaces. Among these coating properties, antistatic properties are particularly important for preventing static electricity on plastic surfaces and on glass surfaces such as cathode ray tubes where static electricity accumulates.

Particularly in the case of cathode ray tubes, as mentioned in the afterword, with the recent spread of computerization, the number of machines in which workers operate near or in contact with the cathode ray tubes has increased, causing eye strain due to viewing the screen and electrostatic shock when touching the tubes. The problem has been highlighted as an operational obstacle.

In response to these problems, coating compositions obtained by hydrolyzing the hydrolyzable silicon compounds described above have been proposed, but conventional coating compositions of this type do not have antistatic properties. One problem is that it cannot maintain its properties over a long period of time and deteriorates over time. Furthermore, since the antistatic property depends on the temperature of the outside world (atmosphere), there is a problem in its effectiveness when used in dry periods or in dry regions.

As an improved technique for this, Japanese Patent Application Laid-Open No. 61-16452
No. 1, a cathode ray tube (cathode ray tube) having a dust-proof and antistatic coating film composed of a silicate material and an inorganic metal compound is proposed. However, in this invention, the silicate material is mainly based on lithium-stabilized silica sol, which is an aqueous dispersion, so as pointed out in Utility Model Publication No. 50-26277, it has poor drying properties and becomes fluid after spraying. However, it has the disadvantage that the pattern of the rough surface that is formed becomes rough. Furthermore, since it is water-based, it is repelled by plastic surfaces and does not form a uniform film, which limits its use to glass. Note that in the improved technique described above, it is stated that organic silicates such as tetraethyl orthosilicate can be used in place of the lithium-stabilized silica sol, but tetraethyl orthosilicate is volatile and does not form a silica film like silica sol. Therefore, it is impossible to apply an anti-scald film.

On the other hand, as a method of making the surface of materials such as plastics and glass conductive, it is sufficient to form an electronically conductive film such as SnO□ or InzO3 on the surface of the material, but the film can be formed by vapor deposition or sputtering. Without it, adhesion would be poor and costs would be high, and application to large objects would be impossible. As this type of improved technology, JP-A-61
-26679, 5n02. by coating method. I
Although a method for forming a conductive film of n20 g is disclosed, baking at 500° C. or higher is required to form an inorganic film. Therefore, the base material is limited to heat-resistant inorganic materials, and there is a drawback that it cannot be applied to plastics or the like.

(Problems to be Solved by the Invention) The present inventors have made extensive studies to solve the problems of the prior art described above. As a result, an alcoholic silica sol obtained by cohydrolyzing a hydrolyzable silicon compound and a conductive metal compound that can be co-hydrolyzed with the hydrolyzable silicon compound in an alcohol solvent has a specific conductivity improvement. When compounded with this agent, it has excellent adhesion to the surface of inorganic or plastic substrates, and surprisingly, it is possible to form a film with excellent conductivity at extremely low heating and drying temperatures of around 150°C. They discovered this and completed the present invention.

[Effects of the Invention] (Means for Solving the Problems) To summarize the present invention, the present invention provides the following features: A co-hydrolyzate of an alcoholic silica sol and a metal compound obtained by co-hydrolyzing the compound in an alcohol solvent.

(ii) Fluoride as a conductivity improver.

The present invention relates to an antistatic coating composition comprising:

Hereinafter, the configuration of the present invention will be explained in detail.

The co-hydrolyzate of the alcoholic silica sol and a conductive metal compound of the present invention is prepared by adding a hydrolyzable silicon compound and a conductive metal compound co-hydrolyzable with the silicon compound to -11U in an alcohol solvent. It can be prepared by partially hydrolyzing a predetermined amount of water in the presence or absence of a catalyst.

The alcoholic silica sol-metal compound cohydrolyzate thus prepared is a siloxane, i.e. 5i-
A colloid consisting of a 0-5i chain (or network) in which a part or all of a metal compound is bonded via a Si-0-M bond (hereinafter also referred to as an alcoholic silica sol-metal compound co-hydrolyzate). It is a dispersion liquid, and the particle size of the colloid particles produced is about 50 to 80 particles, and it is a colorless, transparent, and low viscosity liquid.

As the hydrolyzable silicon compound used to prepare the alcoholic silica sol-metal compound co-hydrolyzate, an organic silicate compound represented by the formula % [ ] is used.

Specific examples of the organic silicates mentioned above include, for example, 5
iCff4. Si iOMe) 4. Si (O
CzH514,Si (QC3H71,,5i(OC,
H9)4. iAc:014Si, and condensates thereof, such as Cβ3SiO3iCj23. fcH301
:+S+03t(OCH313, fc2Fsol 3S
iO5i fOc2H5) 3.1Aco) , 5iO
3i(OAc)2. and commercially available ethyl silicate 40 (manufactured by Corcoro ■).

Hydrolysates of these silicon compounds can be easily obtained by a conventionally known method, for example, by adding a predetermined amount of water to an alcohol solvent and reacting in the presence or absence of an acid catalyst. As such acid catalysts, both inorganic and organic acids can be conveniently used; the inorganic acids are preferably hydrochloric acid, sulfuric acid, nitric acid, heptaphosphoric acid, phosphoric acid, etc., and the organic acids are formic acid, acetic acid, etc. , oxalic acid, p-toluenesulfonic acid, and the like are preferably used. The amount of catalyst is usually 1.0 ppm to 5% based on the silicon compound.
degree is preferably adopted. Although the desired product can be obtained even if it is used in an amount exceeding 5%, particularly good results cannot be expected.

The amount of silicon compound added is the solid content (silica content) of the solution 2
It is preferable to add it in an amount of ˜IO weight %. The amount of water to be blended is such that the hydrolysis rate of the silicon compound is 70 to 500.
%, preferably from 100 to 300%. Solvents used include methanol, ethanol,
Alcohols such as propatool and butanol are preferred.

The reaction temperature is preferably room temperature, but a higher temperature may also be used (and the reaction time varies depending on the temperature and amount of catalyst, but is generally 1 to 48 hours).

The present invention is characterized in that when the hydrolyzable silicon compound is hydrolyzed with a predetermined amount of water in an alcoholic medium, a co-hydrolyzable and conductive metal compound is used in combination.

The conductive metal compound used in the preparation of the alcoholic silica sol-metal compound co-hydrolyzate of the present invention includes:
Any compound that ultimately provides a conductive compound may be used (Sn, In, etc.).

Metal chlorides, nitrates, sulfates, carboxylates such as sb,
Typical examples include alkoxides, acetylacetonate complexes, and mixtures thereof.Tin chlorides and alkoxides is preferred. In addition, when the presence or absence of chlorine must be taken into consideration in the treatment process of the coating liquid or the characteristics of the coating, either tin chloride or tin alkoxide may be used. As is well known, gold &: oxides of tin, antimony, and indium have excellent electrical conductivity.

In the present invention, when a co-hydrolyzable metal compound, such as the above-mentioned tin alkoxide, is used, the compound rapidly reacts with water in the presence of water and becomes cloudy, and the above-mentioned hydrolyzable silicon compound Alternatively, it does not co-hydrolyze efficiently with partial condensates of hands (such as ethyl silicate 40). Therefore, in such cases, it is important to control the co-hydrolysis reaction in the manner described below to ensure that the co-hydrolysis reaction is carried out sufficiently.

(]) A hydrolyzable silicon compound is previously hydrolyzed in an alcohol solvent in the presence of a predetermined amount of water to prepare an alcoholic silica sol, and then at least one selected from tin, antimony, and indium is added to the reaction system. Cohydrolysis is carried out by feeding one type of alkoxide in small amounts.

(ii) Water necessary for hydrolysis of the alkoxide of the metal component is supplied little by little into a mixed solution of the alkoxide of the metal component, the alkoxide of silicon, and an alcohol solvent, and the alkoxide of the metal component is preliminarily hydrated. It is prepared by decomposing it and then adding a predetermined amount of water to hydrolyze the silicon alkoxide.

fiii. Water necessary for hydrolyzing the alkoxide of the metal component is supplied little by little into the mixed solution of the alkoxylate of the metal component and an alcohol solvent to preliminarily hydrolyze the alkoxide of the metal component, and then to this reaction system. It is prepared by adding silicon alkoxide and water to hydrolyze the silicon alkoxide.

In addition, as a method for supplying water in the aspect (iii) above, it is preferable to supply water in a gaseous state together with an accompanying gas (for example, N2 gas).

In the present invention, in the cohydrolysis reaction, an antimony compound is added to a metal compound that plays a doping role for these metal compounds, such as a tin compound, in the hope that the antistatic performance will be expressed by the electronic conductivity type. It is effective to use them together.

Regarding the blending ratio of the hydrolyzable silicon compound and the metal compound, increasing the proportion of the metal compound added increases the antistatic effect, but on the other hand, the adhesion to the substrate decreases, and the ability to form a film also decreases. , whitening, etc. may occur, making it impossible to form a uniform film, so these should be taken into consideration when deciding. Generally, the metal oxide obtained from the metal compound is blended in an amount of about IO to 100 parts by weight, preferably 15 to 50 parts by weight, to 100 parts by weight of silica obtained from the hydrolyzable silicon compound.

In addition, when the co-hydrolysis reaction between the hydrolyzable silicon compound and the metal compound is carried out in the presence of an acidic catalyst, an acid such as hydrochloric acid remaining in a catalytic amount in the alcoholic silica sol metal compound co-hydrolyzate produced, When applied, a chemical reaction occurs with the base material surface to activate the base material surface. This allows the coating composition of the present invention to firmly bond to the surface of the substrate. Therefore, carrying out cohydrolysis in the presence of an acidic catalyst is an effective method.

Next, fluoride as an additive for further improving the antistatic ability in the antistatic coating composition of the present invention will be explained.

A coating agent made by adding a reducing agent and fluoride to a metal salt (for example, tin chloride) solution is applied to the glass surface, and this is coated with 6
It is known that a film with low film resistance can be formed by heating to 00°C (Kiln Association 66 [7],
1958, pp. 52-53). However, the mechanism of action of fluorine in this technology is unknown, and high temperature firing is required.
Moreover, the film formed is also opaque.

In contrast, in the present invention, in the alcoholic silica sol-metal compound co-hydrolyzate, for example, when the metal compound is tin chloride (SnC1!), the tin chloride component is replaced with fluoride to exhibit conductivity in a low temperature range. Tin oxide (S
Fluoride is used from the viewpoint of forming an intermediate that is easily converted to nO□). Further, fluoride is used from the viewpoint that the fluoride forms electronically conductive tin oxide (SnO□), and the added fluoride also exhibits ion conductive properties.

As demonstrated in the Examples described later, when fluoride is added to the alcoholic silica sol-metal compound co-hydrolyzate, excellent antistatic performance with a surface resistance value of 10'Ω is exhibited.

Fluorides that can be used as antistatic (conductivity) improvers in the present invention include metal fluoride, hydrogen fluoride, ammonium fluoride, etc. It is sufficient to use .5% by weight.

Examples of the metal fluoride mentioned above include aluminum fluoride, potassium fluoride, antimony fluoride, tin fluoride, titanium fluoride, iron fluoride, and sodium fluoride.

The antistatic coating composition of the present invention comprising an alcoholic silica sol-metal compound co-hydrolyzate and a fiil fluoride can be prepared by a conventional coating method, such as a dipping method, a barcoding method, a roll coating method, or a spinner coating method. It can be applied to a glass or plastic surface by a spray method or the like, and can be made into an antistatic transparent inorganic film with excellent adhesion and durability by low-temperature drying or heat treatment at around 150°C. 1986
When the antistatic coating composition of the present invention is spray-coated onto the surface of a cathode ray tube face plate by a method as shown in No. 175686, a coating having both anti-shock properties and robust anti-shock properties is formed on the surface. can be formed.

The mechanism by which the antistatic coating composition of the present invention exhibits the antistatic effect can be explained as follows using FIG.

FIG. 1 is a conceptual explanatory diagram showing the mechanism by which the antistatic effect is produced when the antistatic coating composition of the present invention is applied to a glass surface.

Generally, glass has an irregular network structure (siloxane network) having fsiO,l-' chains as its basic skeleton, and has hydroxyl groups (OH) on its surface.

On the other hand, the hydrolyzable silicon compound is also oligomerized or made to have a high molecular weight by hydrolysis, and has some silal groups fsi-OHI in the siloxane network. During the gelation process of the alcoholic silica sol, both oxygen atoms of the silicic acid molecules on the glass surface, hydrogen atoms of the silanol groups on the gel body side, and hydroxyl groups on the glass surface and hydrogen atoms of the silanol groups on the gel body side meet at the glass interface, as shown in Figure 1. Hydrogen bonds form with oxygen atoms in the siloxane network, forming a strong bond.

Furthermore, in the co-hydrolysis process with the hydrolyzable silicon compound, at least a portion of the metal compound forms a Si-0-M (M is a metal atom) bond as shown in FIG. is strongly bonded and provides electrical conductivity to its surface. That is, the metal compound forms a strong conductive layer on the glass surface via the alcoholic hydrolyzate of the hydrolyzable silicon compound. At that time, the added fluoride plays a major role in changing the metal compound into an electronically conductive substance during the gelation reaction and in developing the ionic conductivity of the gelled layer.

In addition, when the base material is plastic, the inorganic polymer of the siloxane network during the gelation process of the alcoholic silica sol-metal compound co-hydrolyzate comes to adhere strongly to the plastic surface due to the complexation effect, so the same effect can be applied. A strong conductive layer is formed on the plastic substrate.

(Example) Hereinafter, the present invention will be explained in more detail with reference to Examples.

In addition, in the examples, all compounding ratios are based on weight.

Example 1 72.6 parts of methanol, 7.5 parts of ethyl silicate 40 (partial hydrolyzate of ethyl silicate manufactured by Colcote ■), and 1.7 parts of tin tetrachloride were mixed uniformly, and mixed with 17.5 parts of water and concentrated. 0.45 part of hydrochloric acid was added to perform cohydrolysis, and 0.15 part of antimony chloride was further added to react.

An antistatic coating composition was prepared by adding 15 parts of isopropyl alcohol (IPA), 35 parts of n-butanol, and 0.1 part of ammonium fluoride to 50 parts of the obtained co-hydrolyzed solution.

Apply this antistatic coating composition to 150X80X
It was coated on a 2+am glass plate by a dipping method, and dried and cured at 150° C. for 1 hour using a constant temperature dryer.

Comparative example 1゛.

An antistatic coating composition prepared according to the same procedure as in Example 1 without the addition of ammonium fluoride was applied and cured according to the same procedure as in Example 1.

The coatings obtained in Example 1 and Comparative Example 1 were evaluated regarding the following items. The evaluation was based on the following method.

・The external appearance of the film was visually observed, and those that were transparent and those with O1 whitening were rated as ×.

・Water resistance The film was immersed in hot water at 50°C for 24 hours, and the state of the film was then examined. Those with good coating conditions were rated as ○.

- When cellophane tape was applied on the adhesive film and instantly peeled off, the film was rated ○ if it did not peel off.

・Surface hardness LION eraser No. 50-50, 25 times back and forth (total 50
(times)) and evaluated the scratches.

(Evaluation criteria) No blemishes ×: There are scratches The results are shown in Table 1.

Table 1 Furthermore, the surface resistance value and charge decay time of the coatings (test samples) obtained in Example 1 and Comparative Example 1 were measured. Measure using the following method.

・Measurement of surface resistance value Measurement was carried out using a stack TR-3 model manufactured by Tokyo Denshi ■.

・Measurement of charge decay time A charge of ±5 KV is applied to the test sample, and the decay of this charge (
The decay to zero volts (Ov) was measured over time. 5ta manufactured by Electrotech according to the US IL standard
Measured using a tic Decay Meter.

The surface resistance value and charge decay time were measured at 20°C and 10°C.
It was exposed for 30 days under accelerated conditions of extremely low humidity of ~15% RH and measured over time. As a result, it was found that the surface resistance characteristics and charge decay characteristics of the coating prepared from the antistatic coating composition of Example 1 hardly deteriorated over time. On the other hand, it was found that Comparative Example 1 had poor surface resistance characteristics, and moreover, the charge decay characteristics increased linearly.

Example 2, Comparative Example 2 The antistatic coating composition prepared in Example 1 and Comparative Example 1 was coated on the outer surface of a cathode ray tube face plate.
．． Spray coating using a nozzle with a diameter of 7+l1m,
By heating and drying at ℃ for 1 hour, an anti-scald cathode ray tube face plate having a fine uneven layer on the outer surface of the face plate was prepared.

Regarding each face panel, glossiness, resolution,
Surface resistance value, charge decay time, and surface hardness (eraser test, scratch test) were measured.

However, the evaluation was performed using the following method.

- Glossiness was measured using the JISZ-8471 glossiness measurement method.

・Resolution is Microcopy Re5olutio
n Te5t ChartfNational Bur
eau of 5standards, 1963. A)
The numerical values were visually judged using the . A higher value indicates better resolution.

・Surface resistance value, charge decay time, surface hardness (eraser test)
was measured by the same method as in Example 1 and Comparative Example 1, and the surface hardness (scratching test) was measured using LISK5400 (19791
-6-14 pencil was used and a load of 500 g was applied. After the test, those with no scratches on the film were rated ○, and those with scratches were rated ×.

The results are shown in Table 2.

(Left below) Example 3. Comparative Example 3 An example is shown in which tin alkoxide was used instead of tin tetrachloride in Example 1.

fil 35.2 parts of ethanol and 40 parts of ethyl silicate
3.3 parts of the above were uniformly mixed, and 1.2 parts of water and 2.8 parts of concentrated nitric acid were added thereto for hydrolysis. Next, IPA2
3.0 parts, ethyl acetate 20 parts, cellosolve acetate 1
A diluted solution was prepared by adding 0.0 part (hereinafter referred to as solution A).

(ii) 20.0 parts of n-butanol and 1 part on oxide basis
2.3 parts of n-butoxytin n-butanol solution (5nOz portion: 30%) containing 0% antimony was mixed uniformly, and 0.2 part of concentrated nitric acid was added to carry out the reaction (hereinafter referred to as , the reaction solution prepared by this reaction is called Solution B).

fiiiil Solution B was added to the above solution A over 1 hour. Next, a homogeneous mixture of 4.9 parts of methanol and 0.1 part of ammonium fluoride was added thereto to prepare the intended antistatic coating liquid.

The antistatic coating liquid prepared as described above was applied onto a glass substrate by dipping, dried at 150°C using an electric constant temperature dryer, and the antistatic property, that is, the surface resistance value was measured. .

For comparison, the surface resistance value was similarly measured using a coating liquid consisting of the liquid A and liquid B. The results are shown in Table 3.

Table 3 [Effects of the Invention 1 The antistatic coating composition of the present invention can form a film having high antistatic properties on various substrates by extremely low heat treatment at around 50°C. . In addition, even in accelerated tests under extremely low temperature conditions, the formed film deteriorates rapidly, whereas the surface resistance and charge attenuation performance of conventional films made only of silicon deteriorate rapidly. Never. In reality, it is extremely rare to be exposed to such a low humidity environment, so it can be said that the product of the present invention maintains its effects semi-permanently.

Furthermore, when the antistatic coating composition of the present invention is applied to the surface treatment of a cathode ray tube face plate, for example, it has a high degree of antistatic (antistatic) ability, is alcoholic, has good volatility, and is free flowing after spraying. Therefore, it is possible to form a film with excellent anti-scald properties consisting of a fine uneven pattern. In other words, the present invention makes it possible to impart high antistatic properties (anti-electric shock) and excellent anti-scald properties to the cathode ray tube face plate through a single treatment (single process), making it possible to produce anti-electrostatic cathode ray tubes with high productivity. and can be manufactured.

Furthermore, since the heat treatment temperature of the antistatic coating composition of the present invention is around 150° C., it is possible to form an antistatic coating with excellent surface properties on synthetic resin molded articles.

As described above, the antistatic coating composition of the present invention has great industrial utility value.

[Brief explanation of drawings]

FIG. 1 is a conceptual explanatory diagram showing the mechanism by which the antistatic effect occurs on the glass surface.

Claims (1)

[Claims] 1. (i) an alcoholic silica sol-metal compound co-hydrolyzate obtained by co-hydrolyzing a hydrolyzable silicon compound and a co-hydrolyzable metal compound in an alcohol solvent; (ii) ) A fluoride, an antistatic coating composition comprising: 2. The antistatic coating compound according to claim 1, wherein the hydrolyzable silicon compound is an organic silicate. 3. The antistatic coating composition according to claim 1, wherein the co-hydrolyzable metal compound is a chloride or an alkoxide. 4. The antistatic coating composition according to claim 3, wherein the co-hydrolyzable metal compound is a compound selected from tin, antimony, and indium. 5. Claim 1, wherein the alcoholic silica sol-metal compound is prepared by mixing a hydrolyzable silicon compound or a partial condensate thereof and a co-hydrolyzable metal compound in an alcohol solvent and co-hydrolyzing the mixture. The antistatic coating composition described in . 6. The antistatic coating composition according to claim 5, wherein the co-hydrolyzable metal compound is a chloride of a metal selected from tin, antimony, and indium. 7. Alcoholic silica sol - A metal compound is prepared by supplying a co-hydrolyzable metal compound little by little to the alcoholic silica sol obtained by hydrolyzing a hydrolyzable silicon compound in an alcoholic solvent, and co-hydrolyzing it with the alcoholic silica sol. The antistatic coating composition according to claim 1, which is prepared by cohydrolyzing a hydrolyzable metal compound. 8. The antistatic coating composition according to claim 7, wherein the co-hydrolyzable metal compound is a metal alkoxide selected from tin, antimony, and indium. 9. The antistatic coating composition according to claim 1, wherein the fluoride is selected from metal fluoride, hydrogen fluoride, and ammonium fluoride.